Inductive damping brain sensor

ABSTRACT

Medical diagnostic devices and related methods of use are described in which one or multiple coils in a sensor, each coil connected with an RLC circuit and frequency counter, are held against a patient&#39;s head at predetermined cranial locations. Frequencies of the RLC circuit are measured and compared against those taken from known, control heads, to determine whether there is a medical problem and what type of problem. In some instances, too high of frequencies can reveal pooled blood in the head, a sign of hemorrhagic stroke, while too low of frequencies imply lack of blood supply, a sign of ischemic stroke. A head-mountable frame can assist a first responder in securing and guiding the coils and, along with fiducials, allow for automatic comparison of frequencies with the correct control data.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/978,437, filed Feb. 19, 2020, which is hereby incorporated byreference in its entirety for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

NOT APPLICABLE

BACKGROUND 1. Field of the Art

Embodiments of the present invention generally relate to diagnosticinstruments, implements, and processes using magnetic field sensors forin vivo measurements. Specifically, they relate to medical devices thatdistinguish between excess fluid in a brain (a possible hemorrhagicstroke), or lack thereof (a possible ischemic stroke), through measuringresonant frequency and damping changes in an electrical circuit coupledwith a magnetic field through the brain.

2. Description of the Related Art

There are two major types of brain strokes. The first is hemorrhagic, inwhich a vessel ruptures in the brain and leads to excessive bleeding.This can compress areas of the brain and prevent adequate perfusion,leading to cell death. The second type is ischemic, in which an embolus,thrombus, or plaque block a blood vessel and lead to decreased bloodflow and cell death.

These two types of strokes are extremely time dependent and have vastlydifferent treatments. For example, for a hemorrhagic stroke, treatmentsinclude administering a drug to counteract blood thinners, drainingblood from the subject's brain through surgery, clamping an aneurysmthrough surgery, filling the aneurysm through endovascular embolization,performing surgery to remove an arteriovenous malformation (AVM), orstereotactically focusing radiation at a blood vessel malformation. Incontrast, for an ischemic stroke, treatments include administeringrecombinant tissue plasminogen activator (tPA) or performing surgery toremove a clot.

If a hemorrhagic stroke is mistaken for an ischemic stroke and treatedas such, for example by administering blood thinners, then the patientcan bleed out. That is, the patient can bleed uncontrollably and die. Itcan be critical for responders distinguish between a hemorrhagic andischemic stroke lest they make the problem worse.

Current means for diagnoses includes computed tomography (CT) scansand/or magnetic resonance imaging (MRI) imaging of a patient's head.Both of these methods are expensive and take precious time. AdditionallyCT scans use ionizing radiation to image the brain; studies have shownthat up to 2% of the cancers that arise each year could be due to CTscan radiation.

There is a need in the art for alternative technologies and methods todistinguish between hemorrhagic and ischemic strokes, as well as detectabnormal fluid densities in the brain.

BRIEF SUMMARY

A medical diagnostic device is described for stroke differentiation andother diagnostics in the brain. The device includes a multi-coil sensorhaving corresponding resistive, inductive, and capacitive (RLC) circuitsand frequency counters attached to respective coils. When positioned ata cranial position on a subject's head, a frequency of the RLC circuitis measured and compared with frequencies taken with the sensor from oneor more known, nominal heads. If the frequency is too high, then ahemorrhagic stroke is indicated. If the frequency is too low, then anischemic stroke is indicated. Power measurements can also be taken todetermine damping, or resistivity, in the brain.

The device can be moved from location to location on the head, coupledwith a wearable frame that ensures accurate positioning. The frame caninclude fiducial elements read by the device so that it automaticallydetermines where its position is on the head and looks up, fromelectronic memory, associated frequencies for the position.

Some embodiments of the present invention are related to an inductivesensor apparatus for brain diagnostics, such as stroke triage, includinga first sensor coil connected with a first resistive, inductive, andcapacitive (RLC) circuit and first frequency counter, a second sensorcoil connected with a second RLC circuit and second frequency counter,the second sensor coil having a larger or smaller diameter than thefirst sensor coil, the first and second sensor coils forming a sensorunit, a memory storing control values derived from prior sensor coilmeasurements of one or more normal brains in vivo, each control valueassociated with a corresponding cranial location, a computer processoroperatively connected with a machine-readable non-transitory mediumembodying information indicative of instructions for causing thecomputer processor to perform operations including generating measurevalues based on outputs from the first and second frequency counterswhen the sensor unit is at a cranial location, determining the craniallocation at which the measured values are associated, retrieving, fromthe memory, control values associated with the cranial location,comparing the measured values to the control values to generate deltas,comparing the deltas to a positive threshold and a negative thresholdassociated with each cranial location to ascertain an exceedance, theexceedance having a sign and a magnitude, and outputting an indicationbased on the sign of the exceedance, and an indicator or displayconnected with the computer processor for the indications.

The operations can further include combining an exceedance from thefirst sensor coil with an exceedance from the second sensor coil togenerate the indication. The indication can include the magnitude of theexceedance.

The apparatus can further include a position gauge attached to thesensor unit, wherein the determining of the cranial location at whichthe measured values are associated includes reading from the positiongauge. It can further include a head-mounting frame including fiducialmarkers indicating cranial locations, wherein the position gauge isconfigured to identify cranial locations based on the fiducial markers.The apparatus can further include an attachment point on thehead-mounting frame configured to releasably connect with the sensorunit. The attachment point can be configured to guide the first andsecond coils of the sensor unit in a direction normal (perpendicular)from a surface at the cranial location.

The apparatus can further include an accelerometer or gyroscopeconnected with the sensor unit and configured to determine the craniallocation at which each measured value is taken. The operations canfurther include generating a matrix of exceedances based on measuredvalues from multiple cranial locations. The operations can furtherinclude rendering an image based on the matrix of exceedances. Theapparatus can further include a temperature sensor connected with thecomputer processor, wherein the operations further comprise compensatingthe measured values for temperature.

The second sensor coil can be coaxial around a common axis with thefirst sensor coil. An exceedance based upon a frequency higher than acontrol value can indicate a hemorrhagic stroke, and an exceedance basedupon a frequency lower than a control value can indicate an ischemicstroke

Some embodiments are related to a method of diagnosing an issue in asubject's brain, such as identifying and distinguishing between anischemic and hemorrhagic stroke, the method including reading a measuredvalue from a first frequency counter on a first resistive, inductive,and capacitive (RLC) circuit connected with a first sensor coil, readinga measured value from a second frequency counter on a second RLC circuitconnected with a second sensor coil, the second sensor coil beingcoaxial around a common axis with the first sensor coil and having alarger or smaller diameter than the first sensor coil, the first andsecond sensor coils forming a sensor unit, the sensor unit held to asubject's head, determining a cranial location at which the measuredvalues are read, retrieving, from a memory, control values associatedwith the cranial location, comparing the measured values with thecontrol values to generate deltas, comparing each delta of the deltas toa positive threshold and a negative threshold in order to ascertain anexceedance, the exceedance having a sign and a magnitude, andindicating, to a user, a possible hemorrhagic or ischemic stroke basedon the sign of the exceedance.

The method can further include indicating, to the user, the magnitude ofthe exceedance. The determining of the cranial location can includereading from a position gauge. The method can further include moving thesensor unit in a direction normal from a surface at the craniallocation. The determining of the cranial location can include readingfrom an accelerometer or gyroscope connected with the sensor unit. Themethod can further include generating a matrix of exceedancescorresponding to multiple cranial locations and rendering an image basedon the matrix of the exceedances.

Some embodiments are related to a method of diagnosing an issue, such asa stroke, in a subject's brain, the method including holding, at acranial location of a subject's head, a sensor unit, the sensor unitincluding a first sensor coil connected with a first resistive,inductive, and capacitive (RLC) circuit and first frequency counter anda second sensor coil connected with a second RLC circuit and secondfrequency counter, activating the sensor unit through an apparatus thatcompares measured values based on frequencies from the sensor unit tostored control values associated with the cranial location, generatesdeltas based on the comparison, compares the deltas to positive andnegative thresholds associated with the cranial location to ascertainsexceedances, each exceedance having a sign and a magnitude, reading anindication from the apparatus based on a sign of an exceedance, andtreating the subject based on the exceedance.

The exceedance can indicate a hemorrhagic stroke, the method furtherincluding treating the subject by administering a drug to counteractblood thinners, draining blood from the subject's brain through surgery,clamping an aneurysm through surgery, filling the aneurysm throughendovascular embolization, performing surgery to remove an arteriovenousmalformation (AVM), or stereotactically focusing radiation at a bloodvessel malformation.

The exceedance can indicate an ischemic stroke, the method furtherincluding treating the subject by administering recombinant tissueplasminogen activator (tPA), or performing surgery to remove a clot.

An exceedance based upon a frequency higher than a control value canindicate a hemorrhagic stroke, wherein an exceedance based upon afrequency lower than a control value can indicate an ischemic stroke.

The exceedance can indicate brain cancer, the method further includingperforming surgery to remove a tumor, administering radiotherapy, oradministering chemotherapy. The exceedance can indicate hydrocephelus,the method further including performing surgery to place a shunt, ordraining fluid from the brain. The exceedance can indicate a vascularabnormality, the method further including performing surgery to correctthe vascular abnormality. The exceedance can indicate neurodegeneration,the method further including administering a drug to the subject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a multi-coil diagnostic device in accordance with anembodiment.

FIG. 2 illustrates the device of FIG. 1 held against a skull of apatient.

FIG. 3 illustrates the device of FIG. 1 releasably connected with acranial positioning frame in accordance with an embodiment.

FIG. 4A is a map showing the cranial location of exceedances for a largecoil in accordance with an embodiment.

FIG. 4B is a map showing the cranial location of exceedances for amedium coil in accordance with an embodiment.

FIG. 4C is a map showing the cranial location of exceedances for a smallcoil in accordance with an embodiment.

FIG. 5 is a map showing the cranial location of exceedances combinedfrom FIGS. 4A-4C in accordance with an embodiment.

FIG. 6 is a three-dimensional (3D) rendering of a location of theexceedances mapped in FIG. 5 .

FIG. 7A is a cross section image from a CT scan from the back of thepatient whose head was measured for FIG. 6 .

FIG. 7B is a cross section image from a CT scan from the left side ofthe patient measured for FIG. 6 .

FIG. 7C is a cross section image from a CT scan from the top of thepatient measured for FIG. 6 .

FIG. 8 is a map showing cranial location of exceedances in anotherpatient in accordance with an embodiment.

FIG. 9 is a three-dimensional (3D) rendering of a location of theexceedances mapped in FIG. 8 .

FIG. 10A is a cross section image from a CT scan from the back of thepatient whose head was measured for FIG. 8 .

FIG. 10B is a cross section image from a CT scan from the top of thepatient measured for FIG. 8 .

FIG. 11 is a map showing cranial location of exceedances in yet anotherpatient in accordance with an embodiment.

FIG. 12 is a three-dimensional (3D) rendering of a location of theexceedances mapped in FIG. 11 .

FIG. 13A is a cross section image from a CT scan from the left side ofthe patient whose head was measured for FIG. 11 .

FIG. 13B is a cross section image from a CT scan from the top of thepatient measured for FIG. 11 .

FIG. 14A illustrates magnetic coupling in a model of a coil and targetin accordance with an embodiment.

FIG. 14B is an equivalent circuit for the model in FIG. 14A.

FIG. 15 illustrates reading control values for a particular craniallocation from a computer memory in accordance with an embodiment.

FIG. 16 illustrates the calculation of deltas and exceedances inaccordance with an embodiment.

FIG. 17 is a flowchart illustrating a process in accordance with anembodiment.

FIG. 18 is a flowchart illustrating a process in accordance with anembodiment.

DETAILED DESCRIPTION

An inductive sensor for the human brain compares measured values tothose acquired from known, control brains taken in the same position onthe head. Any measured value outside of normal ranges can indicate toomuch or too little blood in the measured area. Too much blood in thebrain is a symptom of a hemorrhagic stroke, while too little is asymptom of an ischemic stroke. The sensor can let the user know whichtype of stroke may be and approximately where it is located.

Unlike a traditional electronic crack detection (ECD) sensor used inindustry, which consist of a bridge circuit that measures its sensorcoil impedance, present embodiments have the sensor coil paired with acapacitor to form an electrical resonant circuit. When a conductivetarget, such as blood, is placed in front of the coil, eddy currents aregenerated in the target and produce a counteracting magnetic field. Thiscounteracting magnetic field causes a decrease in the coil inductance,or equivalently, a rise in the coil resonant frequency that can bemeasured by a precise frequency counter.

The same counteracting magnetic field in the target also imposes anelectromotive force that impedes the current flow in the coil, thusincreasing the sensor coil's alternating current (AC) resistance. Thechange in coil resistance can be determined by measuring the powerdissipation in the coil with a precise power meter. The parallelresistance (R) of the resonant inductive-capacitive (LC) tank isinversely related to the coil's AC resistance by R.

U.S. Patent Application Publication No. US 2020/0082926 A1, publishedMar. 12, 2020, further describes fundamentals of an inductive dampingsensor and is incorporated herein by reference.

A technical advantage of the resonant circuit is low power consumption.This can be of great importance for wearable or otherwise portable,battery-powered sensors. Assuming the skull can be modeled as a flat,two-layer structure (see FIG. 14A), then the coil's AC resistance isrelated to the tissue conductivity implicitly and can be modeled by aset of analytical solutions.

FIG. 1 illustrates multi-coil diagnostic device 100 in accordance withan embodiment. Around central, common axis 102 are situated coaxialsensor coils 114, 116, and 118. Each sensor coil 114, 116, and 118 hasan insulated wire coiled in a tight helical shape so that each wrapround has the same diameter. Sensor coil 114 has the smallest diameter,diameter 124. Sensor coil 116 has medium diameter 126, and sensor coil118 has large diameter 128. Sensor coils 114, 116, and 118 are referredto as small, medium, and large coils.

The design of the sensor may use a variety of sizes and shapes. One ormultiple coils may be arranged together to form a device. The coils maybe of different diameters, heights, and/or lengths. The “diameter” maythen refer to a nominal or average diameter. The coils can havedifferent thicknesses of wire and different shapes (e.g., solenoid,circular, spiral, planar, frustum). Variously sized coils may allow forvarying spatial, temporal, and depth resolution.

No common axis is necessary for the coils to share. The coils can beoffset from one another, and no two coils need share the same axis.There can be more than two coils, such as three, four, five, or ‘N’coils. None need be concentric or share an axis.

The coils may be made of metal or other conductor with each woundinsulated from each other by an insulator.

Magnetic shielding may be used to protect the coils from internal orexternal signals. Magnetic shielding may be of any size, thickness, ormaterial so long as it serves the purpose of increasing thesignal-to-noise ratio or improving characteristics of the device.

In the exemplary embodiment, each coil is electrically connected to aseparate unit 104 of analog and digital processing components, each witha resistive, inductive, and capacitive (RLC) circuit 106 and frequencycounter 110.

Memory 112 stores programming instructions and control values derivedfrom prior sensor coil measurements of one or more normal brains invivo, along with corresponding cranial location data. That is, data fromprevious measurements of known brains with the same or similar type ofcoil is averaged or otherwise processed to distill normal ranges offrequency and power loss measurements for particular positions on thebrains. Although different people's heads exhibit different magneticinductances based on age, gender, demographics, and even diet or timesince sleep, there are normal ranges of inductance that are relativelystable. A stroke, especially a massive one, changes the inductancesignificantly due to the heavy influence of iron atoms in hemoglobin onmagnetic permeability.

Computer processor 108 reads and writes from memory 112 and executesinstructions described herein. The instructions cause the processor toread measured values from the power meter and frequency counter 110,compare them with control values associated with the cranial location,calculate deltas, and compare the deltas to positive and negativethresholds associate with the cranial location to ascertain anexceedance.

A “computer processor” includes any type of miniature electronic devicewith arithmetic, logic, and/or control circuitry for performing centralprocessing, or a general or specialized digital circuit that performstranslation or reconveying of digital signals using logic or othercomponents, or as otherwise known in the art. For example it can includea traditional processor, a programmable logic controller (PLC), etc.

A “delta” is a difference between two values, or as otherwise known inthe art.

An “exceedance” includes a value that is above a maximum threshold orbelow a minimum threshold, or as otherwise known in the art. Anexceedance can have a sign and a magnitude. The sign can indicatewhether the exceedance is above a positive threshold or below a negativeone.

The computer processor can output the exceedance itself or a simplifiedindication. Indicator 105 can light up or audibly emit a sound to tellan operator of the exceedance. A display may show much more data, asdescribed further below. The processor, memory, and other elements canbe incorporated on a commercial off-the-shelf board.

In prototypes, some of which are described in the figures, the TexasInstruments LDC (inductive to digital converter) 1101 chip was used toconvert signals from coils into computer readouts. However, the samplingrate for this LCD 1101 frequency counter IC chip is limited toapproximately 40 samples per second. In order to navigate thislimitation, heterodyne downshifting was used for a higher frequencyreadout. If a higher sampling rate is required, the coil voltage can beconnected to a frequency mixer and get downshifted to a lower frequencyat approximately 1 kHz. Then the low-frequency signal is sampled by ananalog-to-digital converter, bandpass-filtered, and conditioned bydigital signal processing algorithms to recover the resonant frequency.This method allows a higher sampling rate above 200 samples per second.Each coil is connected to its own LDC 1101 chip, with readout sent to alocal computer in series.

Various other types of sensors may be introduced onto the inductivedamping sensor, such as accelerometer 122, gyroscopes, piezoelectricsensors, or temperature sensor 120. These devices can be used to improvethe overall accuracy or precision of the inductive damping sensor. Forexample, accelerometer 122 can allow for device positioning andtrajectory mapping as the device is moved around the head, whiletemperature sensor 120 can allow for temperature compensation toincrease signal accuracy.

FIG. 2 illustrates device 100 being held against patient's cranium 220.The patient may be seated, lying, or in other positions. A firstresponder, caregiver, physician, or other user may position the deviceaccording to predetermined locations and obtain a result in real-time.

Data obtained by the device may be stored on a local, remote, cloud orcell network. Transmission of data may be through the use of a wire,radio frequency (RF) such as BLUETOOTH® compatible communications,infrared, optical, or otherwise. This can allow for remote diagnosticsbased off of patient data and also the possibility of directly reportinginformation into an electronic medical record (eMR). This would alsoallow for consolidation of data for predictive model creation andanalysis. Artificial intelligence (AI) machine learning algorithms(e.g., neural networks, support vector machines) can be used todifferentiate between different brain conditions and lesions byutilizing the output generated by the device. The algorithms may also beused to predict the depth, location, size, volume, or shape of lesions.

FIG. 3 illustrates head-mounting frame 330 on patient's head 320 towhich device 100 is releasably connected, forming connected system 300.Head-mounting frame 330 includes nonconductive, non-magnetic lateralrails on which attachment points 332 are formed. Each attachment pointcan be a small hole socket, rivet head, or other feature to which amating connector may be rigidly connected.

Near each attachment point 332 is a fiducial marker 334. Each fiducialmarker is different and is associated with a particular position onhead-mounting frame 330. The fiducial markers are small barcodes thatare read by optical position sensor 336 on device 100, which scans thebar code. The processor on device 100 can read from position sensor 336and automatically determine where it is on the head, i.e., at whatcranial location the coils are positioned. This may be usedindependently or in conjunction with other means of determining thecranial location, such as by accelerometers or by user data entry.

Head-mounting frame attachment point 332 may facilitate guiding thesensor device radially, i.e., perpendicular to a surface of the head, inorder to gather more data from the coils. As the coils are moved closeror farther away from the head, they may detect different features ofinterest or gain sensitivity for an area of interest to a user.

Certain devices may automatically traverse the head-mounting frame,automatically taking and reporting measurements as it goes. Regardlessof whether the device is manual or automatic, the device may have one ormultiple points of contact with the head or device frame as scanningoccurs.

From multiple points of measurements over and across the head, a matrixof measurements can be taken. Each measurement value is compared withdata in the normal range for the corresponding cranial location andplus-minus tolerances or other thresholds, and a matrix of exceedancesis generated. The matrix of exceedances can be charted and displayed toa user.

Data acquired may be represented in two-dimensions (2D) orthree-dimensions (3D). 3D image production of brain lesions may providemore clear assessments of lesion location, depth, volume, size, andshape.

FIGS. 4A-4C are maps showing the cranial locations of exceedances for alarge (FIG. 4A), medium (FIG. 4B), and small (FIG. 4C) coils inaccordance with an embodiment.

FIG. 4A shows that the large coil picked up anomalies in the upper righthand side and near the center midline. Exceedance 442 is in the upperright, which denotes the right-front of the brain. Exceedance 440 isnear the center midline, which denotes the top middle of the brain.

FIG. 4B also shows an anomaly in the top right at exceedance 444. It isslightly inward from where exceedance 442 is on FIG. 4A. Revealingly, noanomaly is detected in the medium coil where exceedance 440 is found inthe large coil.

FIG. 4C confirms an anomaly in the top right, at exceedance 446. It isslightly back from where exceedances 442 and 444 are, but close bynonetheless. Like the medium coil, the small coil detects no anomalywhere exceedance 440 is found in the large coil.

FIG. 5 is a map showing the cranial location of exceedances combinedfrom FIGS. 4A-4C in accordance with an embodiment. The exceedancevalues, or rather the percentage-based, normalized exceedances from thedifferent matrices, are averaged together to form the combined matrix.The averaged exceedances omit exceedance 440 (FIG. 4A) as an outlier andcombine exceedances 442, 444, and 446 from the coils as exceedance 550.

In some embodiments, different weights are given to each of the coils'exceedance values before summing to average. The weights may be based onthe relative “antenna pattern”-like lobe strengths from the respectivecoils. For example, the large coil may have a narrow magnetic field thatgoes relatively deep into the brain, while the small coil has a widermagnetic field that is shallow.

FIG. 6 is a three-dimensional (3D) rendering 650 of a location of theexceedances on a graphic of a patient's head. Volume 650 is plotted toshow a user approximately where there may be a problem in the brain.Data for plotting the volume came from the three different coils.

FIGS. 7A-7C are CT scans for the actual patient from which data forFIGS. 4A-5 were measured. This is the “truth data.” The CT scans confirmthat there is a problem in the patient's brain, a large volume 750 thatis filled with blood. It was caused by a hemorrhagic stroke.

A technical advantage of some embodiments is that they employ relativelysimple and low cost coils to achieve a fast diagnosis of whether thereis a stroke and what type of stroke it is. The device can be maderelatively inexpensively and thus be available more widely, such as innursing homes and outpatient clinics. In contrast, a CT scanner can costtens of thousands of U.S. dollars for refurbished equipment totwo-and-a-half million for a new machine. MRI machines can cost evenmore. Both CT and MRI machines require specialized expertise to use. Itis hoped that the relatively simplicity of present embodiments may notrequire much training, and perhaps require no training similar to thatof automatic defibrillator machines.

FIG. 8 is a map showing cranial location of exceedances in anotherpatient in accordance with an embodiment. An anomaly is detected nearthe midline toward the back, shown as exceedance 850.

FIG. 9 is a three-dimensional (3D) rendering of a location of theexceedances mapped in FIG. 8 . In this case, the smaller coil, whichdetects shallower fluid, detected more of an exceedance than the othercoils and thus volume 950 of interest is shown closer to the scalp. The3D rendering can be panned and rotated so that a physician can determinewhere the blood is located and narrow down what caused it.

FIGS. 10A-10B are truth data CT scans of the patient from which data forFIG. 8 was measured. The CT scans confirm that there is a problem in thepatient's brain on the right side, a large volume 1050 filled withblood. As indicated in the data, the frequencies were higher thannormal, indicating a hemorrhagic stroke.

FIG. 11 is a map showing cranial location of exceedances in yet anotherpatient in accordance with an embodiment. An anomaly on the left sidenear the center is shown as exceedance 1150

FIG. 12 is a three-dimensional (3D) rendering of a location of theexceedances mapped in FIG. 11 , this time showing region 1250 above theleft ear of the patient.

FIGS. 13A-13B are truth data CT scans of the patient from which data forFIG. 11 was measured. The CT scans confirm that there is a problem inthe patient's brain on the left side. In this case, it is an extremelylarge volume 1350 that lacks sufficient blood. The staunched flowreaches all the way to the cranium. The coils detected an issue througha centroid of the volume, which is just over the ear as shown in theprevious figure. As indicated in the data, the frequencies were lowerthan normal, indicating an ischemic stroke. Thus, blood thinners may bean option for this stroke patient.

FIG. 14A illustrates magnetic coupling in a model of a coil and targetin accordance with an embodiment. The coil is modeled as having currenti₁ and producing magnetic field Hi. This creates magnetic coupling Mbetween it and a target. The target is a human head, modeled as a flat,two-layer structure with its own current i₂ and induced magnetic fieldHz. Note that currents i₁ and i₁ are in opposite directions.

FIG. 14B illustrates equivalent circuits for the model in FIG. 14A. RLCcircuit 106 includes a coil modeled with current i₁ running throughinductor Lc with resistance Rc and capacitance C. The coil is connectedto a voltage source providing Vi alternating current. Parasitics ofconnections are modeled as resistances R_(p1) and R_(p2) and inductancesL_(p1) and L_(p2).

Frequency counter 1410 and power meter 1411 are shown, from whichmeasured values can be taken, recorded, compared, and used to indicateanomalies. Data may be converted in an analog-to-digital (A/D) converterand read into a computer processor.

The coil is connected through magnetic coupling M to patient head 1420.Head 1420 includes eddy current i₂ running through an idealized resistorRt (target) and inductor Lt.

FIG. 15 illustrates reading control values for a particular craniallocation from a computer memory in accordance with an embodiment. Theremay be many, many different positions, but for clarity the figure showsan 8×8 grid. Associated with each position are control values for theS(mall), M(edium), and L(arge) coils. Once a cranial position is known,the corresponding values from memory may be extracted and compared withmeasured values.

FIG. 16 illustrates the calculation of deltas and exceedances inaccordance with an embodiment. The vertical axis is frequency, but theactual measured values can represent calibrated frequency, derivedmeasurements, or other values based on frequency and/or resistancemeasured in the coils. Data for each of the coils is plotted across thechart.

For the S(mall) coil, the normal range is plotted as minimum controlvalue 1660 and maximum control value 1662. These may correspond toactual values measured in normal brains, or they may be derived fromstatistical comparisons of many normal (and abnormal) brains andadjusted for standard deviations, tolerances in equipment, etc. An ‘X’marks the measured frequency for the coil, which in the case of thesmall coil is above maximum control value 1662. A difference between themeasured value (X) and maximum control value 1662 is calculated as delta1664, a.k.a. ΔS. Similarly for the other coils, ΔM and ΔL are alsocalculated.

The deltas ΔS, ΔM, and ΔL are compared against respective thresholds forthe cranial location to compute exceedances. For example, ΔS and ΔM areabove and outside of the normal ranges by a large margin and thus areclassified as exceedances. Meanwhile, ΔL is within the normal range andis not classified as an exceedance.

The exceedances for ΔS and ΔM are positive, that is, above the maximumthreshold above the control values. Besides a magnitude, they each havea positive sign to indicate that they are above the control values. Thissign may be used to distinguish between a hemorrhagic and ischemicstroke.

Aside from strokes, the sensor may also be used for detecting traumaticbrain injury, non-stroke hemorrhages in the brain, arteriovenousmalformations (AVMs), benign or malignant brain tumors, and degenerativebrain diseases.

Some embodiments can differentiate between lesion subtypes (i.e.,ischemic and hemorrhagic strokes) based off whether the measuredcurrent, voltage, conductivity, impedance, eddy current, magnetic field,or resistance have increased or decreased with respect to normal brainsor with respect to time. This would allow for differentiation betweenischemia and a hemorrhage based on the direction and/or magnitude of thesensor signal.

Some embodiments may be scanned in the direction normal to the head(i.e., z-axis) to gain information about a brain lesion. Aside frommovements in the direction tangential to the each (i.e., the x-axis andy-axis), the device may be moved in the z-direction to further obtaindepth information regarding the lesion. Movement in the z-direction mayalso allow for varying spatial, temporal, and depth resolution.

To make these measurements, the device may be moved manually, such asbeing held or controlled by an operator, or the device may beautomatically moved by computer controlled motors around the head forscanning. Automation may be due to an internal or external motor.

FIG. 17 is a flowchart illustrating method 1700 of distinguishingbetween ischemic and hemorrhagic strokes in a subject's brain. Inoperation 1701, a measured value is read from a first frequency counteron a first resistive, inductive, and capacitive (RLC) circuit connectedwith a first sensor coil. In operation 1702, a measured value is readfrom a second frequency counter on a second RLC circuit connected with asecond sensor coil, the second sensor coil being coaxial around a commonaxis with the first sensor coil and having a larger or smaller diameterthan the first sensor coil, the first and second sensor coils forming asensor unit, the sensor unit held to a subject's head. In operation1703, a cranial location at which the measured values are read isdetermined. In operation 1704, control values associated with thecranial location are retrieved from a memory. In operation 1705, themeasured values are compared with the control values to generate deltas.In operation 1706, each delta is compared to a positive threshold and anegative threshold in order to ascertain an exceedance, the exceedancehaving a sign and a magnitude. In operation 1707, a possible hemorrhagicor ischemic stroke is indicated to a user based on the sign of theexceedance.

FIG. 18 is a flowchart illustrating method 1800 of diagnosing a strokein a subject's brain. In operation 1801, a sensor unit is held at acranial location of a subject, the sensor unit including a first sensorcoil connected with a first resistive, inductive, and capacitive (RLC)circuit and first frequency counter and a second sensor coil connectedwith a second RLC circuit and second frequency counter. In operation1802, the sensor unit is activated through an apparatus that comparesmeasured values based on frequencies from the sensor unit to storedcontrol values associated with the cranial location, generates deltabased on the comparison, and compares the deltas to positive andnegative thresholds associated with the cranial location to ascertainexceedances, each exceedance having a sign and a magnitude. In operation1803, an indication based on a sign of an exceedance is read from theapparatus, wherein an exceedance based upon a frequency higher than acontrol value indicates a hemorrhagic stroke, and an exceedance basedupon a frequency lower than a control value indicates an ischemicstroke. In operation 1804, the subject is treated based on the sign ofthe exceedance.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

Unless otherwise stated, all measurements, values, ratings, positions,magnitudes, sizes, and other specifications that are set forth in thisspecification, including in the claims that follow, are approximate, notexact. They are intended to have a reasonable range that is consistentwith the functions to which they relate and with what is customary inthe art to which they pertain. “About” in reference to a temperature orother engineering units includes measurements or settings that arewithin ±1%, ±2%, ±5%, ±10%, or other tolerances of the specifiedengineering units as known in the art.

The scope of protection is limited solely by the claims that now follow.That scope is intended and should be interpreted to be as broad as isconsistent with the ordinary meaning of the language that is used in theclaims when interpreted in light of this specification and theprosecution history that follows and to encompass all structural andfunctional equivalents.

Except as stated immediately above, nothing that has been stated orillustrated is intended or should be interpreted to cause a dedicationof any component, step, feature, object, benefit, advantage, orequivalent to the public, regardless of whether it is or is not recitedin the claims.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”or any other variation thereof, are intended to cover a non-exclusiveinclusion, such that a process, method, article, or apparatus thatcomprises a list of elements does not include only those elements, butmay include other elements not expressly listed or inherent to suchprocess, method, article, or apparatus. An element proceeded by “a” or“an” does not, without further constraints, preclude the existence ofadditional identical elements in the process, method, article, orapparatus that comprises the element.

The Abstract is provided to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. In addition, in the foregoing DetailedDescription, it can be seen that various features are grouped togetherin various embodiments for the purpose of streamlining the disclosure.This method of disclosure is not to be interpreted as reflecting anintention that the claimed embodiments require more features than areexpressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed embodiment. Thus the following claims are herebyincorporated into the Detailed Description, with each claim standing onits own as a separately claimed subject matter.

What is claimed is:
 1. An inductive sensor apparatus for braindiagnostics comprising: a first sensor coil connected with a firstresistive, inductive, and capacitive (RLC) circuit and first frequencycounter; a second sensor coil connected with a second RLC circuit andsecond frequency counter, the second sensor coil having a larger orsmaller diameter than the first sensor coil, the first and second sensorcoils forming a sensor unit; a memory storing control values derivedfrom prior sensor coil measurements of one or more normal brains invivo, each control value associated with a corresponding craniallocation; a computer processor operatively connected with amachine-readable non-transitory medium embodying information indicativeof instructions for causing the computer processor to perform operationscomprising: generating measure values based on outputs from the firstand second frequency counters when the sensor unit is at a craniallocation; determining the cranial location at which the measured valuesare associated; retrieving, from the memory, control values associatedwith the cranial location; comparing the measured values to the controlvalues to generate deltas; comparing the deltas to a positive thresholdand a negative threshold associated with each cranial location toascertain an exceedance, the exceedance having a sign and a magnitude;and outputting an indication based on the sign of the exceedance, and anindicator or display connected with the computer processor for theindications.
 2. The apparatus of claim 1 wherein the operations furthercomprise: combining an exceedance from the first sensor coil with anexceedance from the second sensor coil to generate the indication. 3.The apparatus of claim 1 wherein the indication includes the magnitudeof the exceedance.
 4. The apparatus of claim 1 further comprising: aposition gauge attached to the sensor unit, wherein the determining ofthe cranial location at which the measured values are associate includesreading from the position gauge.
 5. The apparatus of claim 4 furthercomprising: a head-mounting frame including fiducial markers indicatingcranial locations, wherein the position gauge is configured to identifycranial locations based on the fiducial markers.
 6. The apparatus ofclaim 5 further comprising: an attachment point on the head-mountingframe configured to releasably connect with the sensor unit.
 7. Theapparatus of claim 6 wherein the attachment point is configured to guidethe first and second coils of the sensor unit in a direction normal froma surface at the cranial location.
 8. The apparatus of claim 1 furthercomprising: an accelerometer or gyroscope connected with the sensor unitand configured to determine the cranial location at which each measuredvalue is taken.
 9. The apparatus of claim 1 wherein the operationsfurther comprise: generating a matrix of exceedances based on measuredvalues from multiple cranial locations.
 10. The apparatus of claim 9wherein the operations further comprise: rendering an image based on thematrix of exceedances.
 11. The apparatus of claim 1 wherein the secondsensor coil is coaxial around a common axis with the first sensor coil.12. The apparatus of claim 1 wherein an exceedance based upon afrequency higher than a control value indicates a hemorrhagic stroke,and an exceedance based upon a frequency lower than a control valueindicates an ischemic stroke.
 13. A method of diagnosing an issue in asubject's brain, the method comprising: reading a measured value from afirst frequency counter on a first resistive, inductive, and capacitive(RLC) circuit connected with a first sensor coil; reading a measuredvalue from a second frequency counter on a second RLC circuit connectedwith a second sensor coil, the second sensor coil being coaxial around acommon axis with the first sensor coil and having a larger or smallerdiameter than the first sensor coil, the first and second sensor coilsforming a sensor unit, the sensor unit held to a subject's head;determining a cranial location at which the measured values are read;retrieving, from a memory, control values associated with the craniallocation; comparing the measured values with the control values togenerate deltas; comparing each delta to a positive threshold and anegative threshold in order to ascertain an exceedance, the exceedancehaving a sign and a magnitude; and indicating, to a user, a type ofissue based on the sign of the exceedance.
 14. The method of claim 13further comprising: indicating, to the user, the magnitude of theexceedance.
 15. The method of claim 13 wherein the determining of thecranial location includes reading from a position gauge.
 16. The methodof claim 13 further comprising: generating a matrix of exceedancescorresponding to multiple cranial locations; and rendering an imagebased on the matrix of the exceedances.
 17. The method of claim 13further comprising: distinguishing between an ischemic and a hemorrhagicstroke based on the sign of the exceedance.